The invention pertains to thermal and mass transport devices.
Micro-channels can provide heat transfer for cooling of, for example, electronic devices such as integrated circuits. While micro-channels can provide enhanced heat transfer, such enhanced heat transfer is generally accompanied by an increase in the pump power needed to force a heat transfer fluid through the micro-channels. In addition, micro-channel based heat sinks typically exhibit significant non-uniformity in heat sink surface temperatures.
Tapered micro-channels can be configured to exhibit a lower cross-sectional thermal resistance at a channel exit than at a channel inlet. Such a configuration can reduce downstream wall surface temperatures, thereby producing a more uniform temperature distribution of the heated surface. However, a decrease in axial channel diameter requires an increase in flow velocity and increased pump power.
In view of these shortcomings, improved heat sinks and thermal management devices and methods are needed.
The present invention provides methods and apparatus that produce, in representative embodiments, increased temperature uniformity of a heated surface while decreasing a pressure drop in an associated heat transfer fluid used to remove heat from the heated surface. Heat transport is achieved with a flow resistance based on a series of consecutively branching flow channels. Such flow channels form branching networks that exhibit efficient transport characteristics similar to those of biological systems.
Thermal management devices (xe2x80x9cTMDsxe2x80x9d) are provided that include an inlet configured to receive a fluid and a branching network situated to receive the fluid from the inlet. The TMDs also include an outlet configured to receive the fluid from the branching network. According to representative embodiments, the branching network includes flow channels corresponding to at least three branching levels. In a particular example, the branching network includes m branching levels having flow channels configured so that             β      =                                    d                          k              +              1                                            d            k                          =                  n                                    -              1                        /            3                                ,          xe2x80x83        ⁢    and              γ      =                                    L                          k              +              1                                            L            k                          =                  n                                    -              1                        /            D                                ,  
wherein dk and Lk are a flow channel diameter and a channel length of a flow channel in a kth branching level, xcex3 and xcex2, are ratios of channel diameters and channel lengths, respectively, n is a number of branches into which a single channel bifurcates, and D is a branching network dimensionality. According to additional examples, the diameters dk are hydraulic diameters and the flow channels are directed substantially radially with respect to the inlet.
According to additional embodiments, TMDs includes a branching network having m branching levels with flow channels configured so that                               L                      k            +            1                                    L          k                    =              n                              -            1                    /          D                      ,          xe2x80x83        ⁢    and                                w                      k            +            1                                    w          k                    =              n                              -            2                    /          3                      ,  
wherein wk and Lk are a flow channel cross-sectional area and a channel length of a flow channel in a kth branching level, respectively, n is a number of branches into which a single channel bifurcates, and D is a branching network dimensionality. In a particular example, D=2 and the flow channels extend along a flow axis.
Heat sinks are provided that include at least one cover layer and a branching network configured to conduct a fluid flow. The branching network is bonded to the cover layer to define flow channels. The cover layer or layers can define a fluid inlet or outlet, and the branching network can be a fractal network.
Thermal management devices are provided that include a branching network pattern layer and first and second cover layers attached to the branching network pattern layer. In representative embodiments, the branching network pattern layer includes m branching levels having flow channels configured so that                               L                      k            +            1                                    L          k                    =              n                              -            1                    /          D                      ,          xe2x80x83        ⁢    and                                w                      k            +            1                                    w          k                    =              n                              -            2                    /          3                      ,  
wherein wk and Lk are a flow channel cross-sectional area and a channel length of a flow channel in a kth branching level, respectively, n is a number of branches into which a single channel bifurcates, and D is a branching network dimensionality.
Heat exchangers are provided that include a cover plate having a heat transfer surface and a branching channel network layer that is bonded to the cover plate. The branching channel network layer is configured to transport a heat transfer fluid to receive heat from the heat transfer surface. In some embodiments, the branching channel network layer defines a fractal flow channel pattern.
Flow networks are provided that include a first branching level that includes at least one first-level flow channel defined by a first set of dimensions and a second branching level that includes second-level flow channels defined by a second set of dimensions. The second branching level includes at least two second-level flow channels for each of the first-level flow channels.
According to a further embodiment, a flow network includes m branching levels having flow channels configured so that                               L                      k            +            1                                    L          k                    =              n                              -            1                    /          D                      ,          xe2x80x83        ⁢    and                                w                      k            +            1                                    w          k                    =              n                              -            2                    /          3                      ,  
wherein wk and Lk are a flow channel cross-sectional area and a channel length of a flow channel in a kth branching level, respectively, n is a number of branches into which a single channel bifurcates, and D is a branching network dimensionality. In a particular example, the flow networks are two dimensional and D=2.
Methods of manufacturing a thermal management device include providing a top layer and a bottom layer and defining a branching network in a branching layer. The top layer is bonded to a first surface of the branching layer and the bottom layer is bonded to a second surface of the branching layer. According to additional embodiments, the branching layer is provided with bridge portions and a perimeter portion wherein the bridge portions and the perimeter portion are configured to interconnect pattern portions corresponding to at least two branching levels. At least a portion of the perimeter portion is removed after the branching network is bonded to either the top layer or the bottom layer. In still further embodiments, a fractal pattern is selected for the branching network.
Fluid mixers include a branching network of fluid channels, wherein the fluid channels are configured to receive at least two fluids. In a specific example, the fluid channels are configured so that                               L                      k            +            1                                    L          k                    =              n                              -            1                    /          D                      ,          xe2x80x83        ⁢    and                                w                      k            +            1                                    w          k                    =              n                              -            2                    /          3                      ,  
wherein wk and Lk are a flow channel cross-sectional area and a channel length of a flow channel in a kth branching level, respectively, n is a number of branches into which a single channel bifurcates, and D is a branching network dimensionality.
These and other features and advantages of the invention are set forth below with reference to the accompanying drawings.